sculpt_manager: start fb on second CPU on Pocket

With this commit the fb driver is started on the second CPU on the
MNT Pocket Reform to decouple it from the other components started
on the first CPU during the system's boot-up and mitigates bring-up
issues with this driver that result in an often non-working display.

Issue #5378.

repos/gems/src/app/sculpt_manager/driver/fb.h

@@ -164,12 +164,16 @@ struct Sculpt::Fb_driver : private Noncopyable
 		                     registry, "vesa_fb", Priority::MULTIMEDIA,
 		                     Ram_quota { 8*1024*1024 }, Cap_quota { 110 });
 
+		Affinity::Location const fb_affinity =
+			board_info.soc.fb_on_dedicated_cpu ? Affinity::Location { 1, 0, 1, 1 }
+			                                   : Affinity::Location { };
+
 		_soc_fb.conditional(board_info.soc.fb && board_info.options.display,
 		                    registry, Child_state::Attr {
 		                        .name      = "fb",
 		                        .priority  = Priority::MULTIMEDIA,
 		                        .cpu_quota = 20,
-		                        .location  = { },
+		                        .location  = fb_affinity,
 		                        .initial   = { Ram_quota { 16*1024*1024 },
 		                                       Cap_quota { 250 } },
 		                        .max       = { } } );

repos/gems/src/app/sculpt_manager/main.cc

@@ -302,7 +302,7 @@ struct Sculpt::Main : Input_event_handler,
 		.modem = false,
 		.nic   = _mnt_reform || _mnt_pocket,
 
-		.fb_on_dedicated_cpu = false
+		.fb_on_dedicated_cpu = _mnt_pocket
 	};
 
 	Drivers _drivers { _env, _child_states, *this, *this };